The invention relates to electron emitters and more particularly to electron emissive materials suitable for use in such structures.
Electron emissive materials are particularly useful for incorporation in detection devices such as, for example, photomultiplier tubes, image tubes, and image intensifier tubes, as photocathodes or secondary emissive electrode materials. The operation and construction of such detection devices is well known in the art of electron discharge devices.
Numerous electron emissive materials and electron emitters including such materials have been developed which are suitable for photocathodes and/or secondary emissive electrodes. Among such materials or emitters are, for example, those described in the following U.S. patents relating to photocathodes and their manufacture:
U.S. Pat. No. 2,676,282 issued to J. J. Polkosky on Apr. 20, 1954;
U.S. Pat. No. 2,770,561 issued to A. H. Sommer on Nov. 13, 1956;
U.S. Pat. No. 2,880,344 issued to R. G. Stoudenheimer on Mar. 31, 1959;
U.S. Pat. No. 2,914,690 issued to A. H. Sommer on Nov. 24, 1959
U.S. Pat. No. 3,697,794 issued to R. G. Stoudenheimer on Oct. 10, 1972;
U.S. Pat. No. 3,372,967 issued to F. R. Hughes on Mar. 12, 1968;
U.S. Pat. No. 3,658,400 issued to F. A. Helvy on Apr. 25, 1972; and
U.S. Pat. No. 3,838,304, issued to A. F. McDonie on Sept. 24, 1974.
Electron emissive materials and electron emitters including such materials have also been developed which relate specifically to secondary emissive electrodes and their manufacture and are, for example, further described in the following U.S. patents:
U.S. Pat. No. 2,881,343 issued to J. J. Polkosky et al. on Apr. 7, 1959; and
U.S. Pat. No. 3,753,023 issued to A. H. Sommer on Aug. 14, 1973.
As indicated in the above-noted patents, the manufacture of electron emitters is a highly developed art in which a considerable effort has been exerted to increase the sensitivity of the known electron emissive materials and to provide desired spectral response characteristics. Typically, base layers of solid antimony which have been sensitized or activated with the vapors of cesium, and/or one or more additional alkali metals have been widely used in electron emitters.